Supercritical Heat Transfer Characteristics of a JP-8 Surrogate Fuel in a Scramjet Regenerative Cooling Channel under Different Heated-Wall Locations

Scramjet engines operating under hypersonic conditions require regenerative cooling using jet fuel to mitigate severe thermal loads. Under supercritical conditions, pronounced variations in thermophysical properties can significantly alter the flow and heat transfer behavior. In this study, the supercritical heat transfer characteristics of JP-8 fuel in a scramjet regenerative cooling channel were numerically investigated using a surrogate fuel formulated via a genetic algorithm. At an operating pressure of 3 MPa, abrupt changes in density and specific heat near the pseudo-critical temperature induce buoyancy effects, leading to buoyancy-driven rotational and secondary flows. The flow and heat transfer characteristics were found to be highly dependent on the heated wall location. In the side-wall heating case, asymmetric rotational flow and isolated dead zones were observed, which were associated with locally unfavorable heat transfer performance. In contrast, the bottom- and top-wall heating cases exhibited enhanced secondary flow development and improved flow mixing. Although the total heat absorbed by the fuel remained similar across all cases, the wall temperature distributions varied markedly depending on the heating configuration. These results demonstrate that buoyancy-driven flow structures play a critical role in determining supercritical heat transfer behavior in regenerative cooling channels.